Method of treating a hydrocarbon chargestock

ABSTRACT

A catalyst composition useful in the catalytic oxidation of mercaptans is disclosed. The composition is a stable aqueous slurry or suspension of a first component which is predominantly a metal phthalocyanine disulfonate compound, and a second component which is predominantly a tetrasulfonated metal phthalocyanine compound.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of copending, commonly assigned application Ser. No.07/176,110 filed Mar. 30, 1988, now U.S. Pat. No. 4,885,268 issued Dec.5, 1989.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to catalyst compositions and,more particularly, the invention relates to a catalyst useful in theconversion of mercaptans to disulfides in petroleum distillatechargestocks.

2. Description of Related Art

The removal of mercaptan sulfur from hydrocarbons, particularlypetroleum distillates, such as cracked gasolines, straight gasolines,etc., is an ongoing problem. Mercaptans are objectionable due to theircorrosive nature and their strong odor.

A well known and generally accepted process for treating hydrocarbonfractions to convert mercaptans to less objectionable disulfides bycatalytic oxidation is the UOP Merox® process. In one form, the Merox®process uses a catalyst which is soluble in caustic solution inliquid-liquid contact with the hydrocarbon fractions.

The type of catalyst most widely used in the Merox® process and similartypes of mercaptan oxidation processes include sulfonated derivatives ofmetal phthalocyanine compounds. Cobalt phthalocyanine sulfonates arepreferred.

The preparation and use of metal phthalocyanine sulfonates having mono-,di-, tri-, and tetra sulfonate functionality is well described in theliterature. See, for example, U.S. Pat. Nos. 3,039,855 (Urban),3,108,081 (Gleim), 4,003,827 (Carlson, et al.), and 4,049,572 (Douglas),all assigned to Universal Oil Products Company, and Fukada, in NipponKagoku Zasshi, Volume 79, at pages 396-399 (1958). Each of the foregoingpatents and publication is incorporated herein by reference.

Metal phthalocyanine sulfonates, in particular cobalt phthalocyaninesulfonates, differ in activity and in their solubility characteristicsdepending at least in part on their respective sulfonatefunctionalities. This has caused a number of problems for users of thesematerials.

For example, cobalt phthalocyanine disulfonate, commonly used inmercaptan oxidation units calling for two phase liquid-liquid contact,was at one time sold in a dry powdered form which was extremely dusty.This was undesirable because cobalt phthalocyanine sulfonates are strongdyes. Several different approaches were attempted in order to eliminatehandling problems, including the packaging of disulfonate material inwater soluble bags; mixing the material with an antidusting agent suchas PTFE; and admixing the disulfonate compound with water and sellingthe product as a slurry.

Although the packaging of cobalt phthalocyanine disulfonate as anaqueous slurry is widely accepted, this approach suffers from severalproblems. With insufficient mixing, the disulfonate materialprecipitates from the slurry. If the slurry is mixed sufficiently toretain the disulfonate in suspension for acceptable lengths of time, theslurry becomes extremely viscous and may gel, making it very difficultto remove the material from packaging.

The use of cobalt phthalocyanine tetrasulfonate, which is highly solublein water, can eliminate the precipitation and gelation problemsassociated with the use of disulfonate slurries. However, reports ofactual operating experience in the field and laboratory tests indicatethat the catalytic activity of the tetrasulfonate form of cobaltphthalocyanine is not as high as that of the disulfonate form.

SUMMARY OF THE INVENTION

It is an object of the invention to overcome one or more of the problemsdescribed above.

According to the invention a stable, fluid (i.e. non-gelatinous) aqueousslurry of metal phthalocyanine sulfonate catalyst is provided. Theinventive catalyst composition has acceptably high activity, with thedesirable stable fluid handling properties associated with prior metalphthalocyanine tetrasulfonate solutions.

The inventive catalyst composition is a stable suspension or slurry of ablend of first and second components, the first component beingpredominantly a metal phthalocyanine disulfonate, and the secondcomponent being predominantly a metal phthalocyanine tetrasulfonate,with a total sulfonate concentration of up to about 3 lbs. per gallon ofslurry or suspension.

Further objects and advantages will be apparent to those skilled in theart from a review of the following detailed description, taken inconjunction with the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention a stable, fluid catalyst composition usefulin, for example, the catalytic oxidation of mercaptans to disulfides inhydrocarbon fractions is provided by forming a slurry or suspension of ablend of first and second metal phthalocyanine sulfonate components. Therespective first and second components may be prepared separately,blended, and subsequently dispersed in water or, alternatively, they maybe coproduced and subsequently dispersed in water.

The first component is predominantly metal phthalocyanine disulfonate,which may be in admixture with mono-, tri-, and tetrasulfonated forms ofthe metal phthalocyanine compound. However, the disulfonate form of themetal phthalocyanine compound should comprise at least 50 wt. % of thesulfonate compounds of the first component.

A typical "spectrum" analysis of disulfonated cobalt phthalocyaninecompounds is given in Example I, Table I of Carlson, et al. U.S. Pat.No. 4,003,827, as follows:

    ______________________________________                                        Isomer          Wt. %                                                         ______________________________________                                        Monosulfonate   6.3                                                           Disulfonate     59.6                                                          Trisulfonate    25.6                                                          Tetrasulfonate  8.5                                                           Total           100.0                                                         ______________________________________                                    

A composition of 60 wt. % disulfonate, 10 wt. % tetrasulfonate, and 30wt. % mono- plus trisulfonate should be considered typical ofcommercially available disulfonated cobalt phthalocyanine compounds.Those skilled in the art, however, will recognize that the actualpercentage ranges will vary in practice, and are exclusive of inertsalts and other diluents which may be present.

The second component of the metal phthalocyanine compound blend ispredominantly the tetrasulfonated isomer of the metal phthalocyaninesulfonate compound. Although it has been reported that tetrasulfonatedmetal phthalocyanine compounds are available in substantially pure form,in practice the second component may contain very small amounts of themono-, di-, and trisulfonate isomers. According to the invention, thetetrasulfonate isomer comprises at least about 99 wt. % of the metalphthalocyanine sulfonates in the second component of the blend,exclusive of inert salts and other diluents which may be present.

The blend of metal phthalocyanine sulfonate components broadly comprisesbetween about 9 and 91 wt. % of the first (predominantly disulfonate)component and, correspondingly, between about 91 and 9 wt. % of thesecond (predominantly tetrasulfonate) component.

It is preferred that the total concentrations of disulfonated andtetrasulfonated metal phthalocyanine compounds (based on total metalphthalocyanine sulfonates in the composition) be in the range of about30 to 55 wt. % disulfonates and at least about 18 wt. % tetrasulfonates,respectively, with a total concentration of mono- and trisulfonates notexceeding about 30 wt. %.

The inventive composition has a concentration of from greater than zeroto about 3 lbs. of total metal phthalocyanine sulfonate compounds pergallon of composition, although a total concentration of about 21/2 lbs.total metal phthalocyanine sulfonate compounds per gallon of compositionmay be the practical maximum for most applications. It is highlypreferred that the metal phthalocyanine sulfonate concentration be inthe range of about 2 to 21/2 lbs. per gallon of slurry or suspension.

The preferred forms of the metal compound used in the invention aresulfonated cobalt phthalocyanine compounds.

The disulfonated isomers may be prepared by processes known in the art,and are commercially available. It is preferred that the tetrasulfonatedisomer be prepared by the method of Fukada, Nippon Kagoku Zasshi, Volume79, at pages 396-399 (1958), the disclosure of which is incorporatedherein by reference, which involves the reaction of a 4-sulfophthaliccompound, a metal salt, and an ammonium donor.

Useful modifications of this procedure are described in Weber and Busch,Inorg. Chem. Vol. 4, at 469-71 and 472-75 (1965), the respectivedisclosures of which are incorporated herein by reference.

An exemplary synthesis reaction scheme uses sulfophthalic acid, urea,cobalt chloride, and an ammonium molybdate catalyst. The sulfophthalicacid is typically used in aqueous solution comprising 50 wt. % water,12.5 wt. % 3-isomer, and 37.5 wt. % 4-isomer.

The catalyst composition of the invention is useful in any of the wellknown liquid-liquid mercaptan oxidation processes using metalphthalocyanine catalysts. For example, the liquid catalyst compositionmay be dissolved in caustic solution with the reaction being carried outat a pH of 8 to 14.

The inventive catalyst composition preferably should not be used intreating certain hydrocarbon fractions that contain components whichextract sulfonated metal phthalocyanine compounds from the causticphase, resulting in high losses of catalyst and discoloration of thechargestock. (Tetrasulfonates are not known to be extractable to asignificant degree.) For example, some gasolines are believed to containglycols which extract disulfonates, and possibly mono- andtrisulfonates, from a caustic phase containing the inventivecomposition.

One surprising aspect of the present invention is the ability to form aslurry or suspension of sulfonated metal phthalocyanine compoundscontaining high concentrations of the disulfonated form of the metalphthalocyanine compound without precipitation of disulfonated metalphthalocyanine material For example, it is possible according to theinvention to prepare compositions wherein the disulfonated materialcomprises up to 55 wt. % of the total sulfonated phthalocyanines withoutexperiencing precipitation, or gelation of the solution upon thoroughmixing.

Furthermore, the catalytic activity of the composition is acceptablyhigh for all commercial applications.

Thus, the desirable mechanical properties of the composition greatlyenhance the material handling characteristics thereof without asacrifice of acceptable catalytic activity.

From the foregoing description, those skilled in the art will appreciatethat the invention comprehends a method of stabilizing metalphthalocyanine disulfonates in a fluid slurry or suspension by blendingor coproduction with tetrasulfonated metal phthalocyanine compounds, inrespective concentrations as taught herein.

The invention further comprehends a method of treating a hydrocarbonfraction such as a petroleum distillate chargestock to catalyticallyoxidize mercaptans wherein the inventive catalyst composition isdispersed in a liquid phase at an alkaline pH which is placed in twophase liquid-liquid contact with the fraction to be treated underappropriate treatment conditions as are well known in the art.Preferably, the composition is dispersed in a caustic phase (pH about 8to 14) and contacted with the chargestock in an oxygen-containingatmosphere at a temperature of about 15° to 300° C. and a pressure ofabout 1 to 100 atmospheres.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications within the scope of the invention will beobvious to those skilled in the art.

I claim:
 1. A method of treating a hydrocarbon chargestock containingmercaptans comprising the steps of:(i) dispersing a catalyst in acaustic aqueous phase, wherein said catalyst comprises a catalystcomposition consisting essentially of a stable fluid slurry orsuspension of a blend of first and second metal phthalocyanine sulfonatecomponents in water, said first component comprising a metalphthalocyanine disulfonate compound, said disulfonate compoundcomprising at least 50 wt. % of the metal phthalocyanine sulfonates insaid first component, said second component comprising a metalphthalocyanine tetrasulfonate compound, said tetrasulfonate compoundcomprising at least 99 wt. % of the total metal phthalocyaninesulfonates in said second component, said second component comprisingbetween about 9 and 91 wt. % of the total of said first and secondcomponents, and the total concentration of said metal phthalocyaninesulfonates being greater than zero and up to about 3 lbs. per gallon ofsaid slurry or suspension; and (ii) contacting said aqueous phase withsaid hydrocarbon chargestock in an oxygen containing atmosphere whereinsaid chargestock is in liquid contact with said aqueous phase.
 2. Themethod of claim 1 wherein said caustic aqueous phase is at a pH of about8 to about
 14. 3. The method of claim 1 wherein said contacting occursat a temperature of about 15° to about 300° C. and said atmosphere is ata pressure of about one to about 100 atmospheres.
 4. The method of claim1 wherein said first and second metal phthalocyanine sulfonatecomponents are cobalt phthalocyanine sulfonate components.
 5. The methodof claim 1 wherein said second component consists essentially of saidmetal phthalocyanine tetrasulfonate compound.
 6. The method of claim 1wherein said catalyst composition includes sulfonated metalphthalocyanine derivatives selected from the group consisting ofmonosulfonates and trisulfonates, with the total concentration of saidmonosulfonates and trisulfonates not exceeding 30 wt. % of totalsulfonated metal phthalocyanine compounds in said composition.
 7. Themethod of claim 1 wherein the total concentration of said first andsecond components is between about 2 and 2.5 lbs. per gallon of saidslurry or suspension.
 8. The method of claim 1 wherein the sulfonatedmetal phthalocyanine compounds in said composition comprise from about30 to about 50 wt. % disulfonated metal phthalocyanine compounds, up toabout 30 wt. % combined mono- and trisulfonated metal phthalocyaninecompounds, and at least 18 wt. % tetrasulfonated metal phthalocyaninecompounds.
 9. A method of treating a hydrocarbon chargestock containingmercaptans comprising the steps of:(i) dispersing a catalyst in acaustic aqueous phase, wherein said catalyst comprises a catalystcomposition consisting essentially of a stable fluid slurry orsuspension of a blend of first and second metal phthalocyanine sulfonatecomponents in water, said first component comprising a metalphthalocyanine disulfonate compound, said disulfonate compoundcomprising at least 50 wt. % of the metal phthalocyanine sulfonates insaid first component, said second component comprising a metalphthalocyanine tetrasulfonate compound, said tetrasulfonate compoundcomprising at least 99 wt. % of the total metal phthalocyaninesulfonates in said second component, said second component comprisingbetween about 9 and 91 wt. % of the total of said first and secondcomponents, and the total concentration of said metal phthalocyaninesulfonates being greater than zero and up to about 3 lbs. per gallon ofsaid slurry or suspension; and (ii) contacting said aqueous phase withsaid hydrocarbon chargestock in an oxygen containing atmosphere, whereinsaid chargestock is in liquid contact with said aqueous phase and saidchargestock is substantially free of components which extract sulfonatedmetal phthalocyanine compounds from said caustic aqueous phase.
 10. Themethod of claim 9 wherein said caustic aqueous phase is at a pH of about8 to about
 14. 11. The method of claim 9 wherein said contacting occursat a temperature of about 15° to about 300° C. and said atmosphere is ata pressure of about one to about 100 atmospheres.
 12. The method ofclaim 9 wherein said components which extract metal sulfonatedphthalocyanine compounds are glycols.
 13. The method of claim 9 whereinsaid first and second metal phthalocyanine sulfonate components arecobalt phthalocyanine sulfonate components.
 14. The method of claim 9wherein said second component consists essentially of said metalphthalocyanine tetrasulfonate compound.
 15. The method of claim 9wherein said catalyst composition comprises sulfonated metalphthalocyanine derivatives selected from the group consisting ofmonosulfonates and trisulfonates, with the total concentration of saidmonosulfonates and trisulfonates not exceeding 30 wt. % of totalsulfonated metal phthalocyanine compounds in said composition.
 16. Themethod of claim 9 wherein the total concentration of said first andsecond components is between about 2 and 2.5 lbs. per gallon of saidslurry or suspension.
 17. The method of claim 9 wherein sulfonated metalphthalocyanine compounds in said composition comprise from about 30 toabout 50 wt. % disulfonated metal phthalocyanine compounds, up to about30 wt. % combined mono- and trisulfonated metal phthalocyaninecompounds, and at least 18 wt. % tetrasulfonated metal phthalocyaninecompounds.